(function (doc, win) {    
        var docEl = doc.documentElement,    
        resizeEvt = 'orientationchange' in window ? 'orientationchange' : 'resize',    
        recalc = function () {    
        var clientWidth = docEl.clientWidth;    
        if (!clientWidth) return;    
        docEl.style.fontSize = 20 * (clientWidth / 320) + 'px';    
    };    
    if (!doc.addEventListener) return;    
    win.addEventListener(resizeEvt, recalc, false);    
    doc.addEventListener('DOMContentLoaded', recalc, false);    
    })(document, window);
